Catalyst compositions especially useful for preparation of unsaturated acids

ABSTRACT

The present invention is a catalyst composition consisting of oxides or oxide complexes that contains catalytically significant amounts of uranium or thorium plus, tungsten, vanadium and molybdenum plus optionally one or more of Co, Ni, Zn, Cu, Mg, Mn, Bi, Ti, Zr, Sn, P, an alkali metal, an alkaline earth metal, lanthanum or an element of the lanthanoid series. These catalysts are especially useful for producing acrylic acid from acrolein and for producing methacrylic acid from methacrolein.

This is a continuation of Ser. No. 507,316 filed Sept. 20, 1974, now abandoned, which is a divisional of Ser. No. 428,267 filed Dec. 26, 1973, now abandoned.

BACKGROUND OF THE INVENTION

Catalyst compositions similar to those of the invention are known, see U.S. Pat. No. 3,567,773 which shows catalysts containing WVMo. The present invention adds uranium or thorium to these catalysts and obtains unexpectedly desirable catalysts for producing acrylic acid and methacrylic acid.

The production of acrylic acid by the oxidation of acrolein and the production of methacrylic acid by the oxidation of methacrolein are known in the art. With respect to these processes, the present invention employs the known art process but substitutes the catalysts of the invention for the catalysts of the art.

SUMMARY OF THE INVENTION

The present invention is a catalyst composition consisting of oxides or oxide complexes that contains catalytically significant amounts of uranium, thorium or mixture thereof, tungsten, vanadium and molybdenum plus optionally one or more of Co, Ni, Zn, Cu, Mg, Mn, Bi, Ti, Zr, Sn, P, an alkali metal, an alkaline earth metal, lanthanum or an element of the lanthanoid series. These catalysts are especially effective for preparing acrylic acid from acrolein and the preparation of methacrylic acid from methacrolein. The catalysts are also highly effective for oxidation reactions such as the oxidation of butadiene to maleic anhydride and the oxidative esterification of unsaturated aldehydes to the corresponding unsaturated ester. The catalysts of the invention are highly reactive and are capable of very selectively oxidizing acrolein to acrylic acid at low temperatures with little or no acetic acid production.

The invention is the catalyst composition. The basic invention is a catalyst containing uranium, thorium or mixture thereof, tungsten, vanadium and molybdenum. The other possible elements of the catalyst are optionally included.

As noted above, catalysts very similar to the catalysts of the invention are known, see for example U.S. Pat. No. 3,567,773. Moreover, catalysts of the general type of the catalysts are known and a person of ordinary skill in the art needs no more than the description of the elements in the catalyst to prepare catalysts claimed by the present invention. Thus, the broad description of the invention makes the catalysts of the invention available.

Normally, the catalysts of the invention are prepared by mixing the catalyst ingredients in the proper proportions in an aqueous mixture, drying the resulting aqueous slurry and calcining the product. The ingredients going into the preparation of the catalysts can be the oxides, halides, nitrates or other salts of the particular compound added. If a support is used, the material comprising the support is usually incorporated into the catalyst along with the other ingredients. After the catalyst ingredients have been combined to form an aqueous slurry, the slurry is evaporated to dryness, and the dried solid obtained is heated in the presence of air at temperatures between about 200° and 600° C. This calcination can take place outside of the catalytic reactor or an in situ activation could be utilized.

Although there are a number of preparations that could be used to make desirable catalysts of the invention, catalysts that contain molybdenum in a partially reduced state below hexavalent molybdenum are preferred. The preparation of catalysts of the invention containing reduced molybdenum is shown in the Specific Embodiments.

The broad composition of the catalyst is described above. With respect to the composition, there are certain preferred embodiments. Preferred are those catalysts wherein more than about 50% of the atoms, exclusive of oxygen and any support material, are molybdenum. Also, with respect to the broad description, those catalysts having no optional components or optional components of Fe, Ni, Co, Zn, Sn, Mn, Mg, Cu or mixture thereof are preferred.

In terms of a specific empirical formula, the catalysts of the invention are described by the following formula:

    A.sub.a D.sub.b W.sub.c V.sub.d Mo.sub.e O.sub.x

wherein

A is Co, Ni, Zn, Cu, Mg, Mn, Bi, Ti, Zr, Sn, P, an alkali metal an alkaline earth metal, lanthanum, an element of the lanthanoid series or mixture thereof; and

D is uranium, thorium or mixture thereof;

and wherein

a is 0 to about 5;

b, c and d are about 0.1 to about 10;

e is a number of about 6 to about 16; and

x is the number of oxygens required to satisfy the valence requirements of the other elements present.

Referring to the formula, preferred catalysts are designated when A is Fe, Ni, Co, Zn, Sn, Mn, Mg, Cu or mixture thereof and when a is greater than zero. Individual optional elements represents by A which are preferred are copper and cobalt.

In addition to the active catalytic ingredients, the catalysts of the invention may contain a support material. Suitable support materials include silica, alumina, zirconia, titania, silicon carbide, boron phosphate and the like. A preferred support material is silica.

As noted above, the catalysts of the invention are useful in a number of different oxidation reactions. Preferred among these reactions is the production of unsaturated acids from the corresponding unsaturated aldehyde. In such a process, acrylic acid or methacrylic acid is produced by reacting acrolein or methacrolein with molecular oxygen in the presence of steam at a temperature of about 200° to about 500° C. Of special interest is the preparation of acrylic acid from acrolein because of the extremely desirable results obtained.

The oxidation of unsaturated aldehydes to obtain the corresponding acid is well known in the art. Basically, the invention, with respect to the process, is the use of the new catalyst within the parameters of the known art process.

The known process involves the contacting of the unsaturated aldehyde with molecular oxygen in the presence of steam at a temperature of about 200° to about 500° C. The ratio of the reactants may vary widely with molar ratios of molecular oxygen to aldehyde of about 0.5 to about 5 moles normally being employed. Molecular oxygen is most conveniently added as air. The amount of steam may vary widely from the small amount generated in the reaction to 20 or more moles of steam per mole of aldehyde. In the preferred practice of the invention, about 1 to about 10 moles of steam are added to the reactant feed.

The reaction may be conducted in a fixed- or fluid-bed reactor using atmospheric, superatmospheric or subatmospheric pressure. The apparent contact time may vary considerably with contact times of a fraction of a second to 20 seconds or more normally being employed.

Using the catalyst of the invention, very desirable yields of unsaturated acid are obtained at low temperatures with the production of little or no acetic acid.

SPECIFIC EMBODIMENTS Comparative Example A and Examples 1-3--Catalyst of Invention Compared to the art

A base catalyst of the invention was prepared and compared to a catalyst of U.S. Pat. No. 3,567,773. The catalysts were prepared as follows:

Comparative Example A 62% W₁.2 V₃ Mo₁₂ O_(x) and 38% SiO₂

This catalyst was prepared according to Example 6 of U.S. Pat. No. 3,567,773.

EXAMPLES 1-3 U₂ W₁.2 V₃ Mo₁₂ O_(x)

An aqueous slurry was prepared in 500 cc. of distilled water. The slurry contained 72.0 g. of MoO₃, 11.36 g. of V₂ O₅ and 9.19 g. of tungsten metal powder. The slurry was refluxed for two hours during which the color of the slurry changed to blue-black.

Separately, 35.3 g. of UO₂ (C₂ H₃ O₂)₂.2H₂ O was dissolved in water and added to the slurry. The resulting mixture was refluxed for one hour, and then evaporated to a paste material. The paste was dried in an oven over night at 110° C. The catalyst was ground and screened to obtain a 10 to 30 mesh fraction.

The catalysts prepared above were placed in a reactor constructed of a 1.0 cm. inside diameter stainless steel tube having a reaction zone of 20 cc. The catalyst of the invention was activated for two hours under an air flow at 400° C. The reactor was fed with a mixture of acrolein/air/steam in the molar ratio of 1/10/6. The temperature of the surrounding heating block and the apparent contact time are given in Table I. The results are also given in Table I using the following definitions: ##EQU1##

                                      TABLE I                                      __________________________________________________________________________     Comparison of CeWVMo with WVMo in the                                          Preparation of Acrylic Acid                                                                         Single Pass Yield, %                                                    Temp.,                                                                             C.T.,                                                                             Acrylic                                                                              Acetic                                              Example                                                                             Catalyst °C.                                                                         Sec.                                                                              Acid  Acid Conversion, %                                                                          Selectivity, %                         __________________________________________________________________________     1    U.sub.2 W.sub.1.2 V.sub.3 Mo.sub.12 O.sub.x                                             271 2.0                                                                               82.5  0.3  100     82.5                                   2    "        246 2.2                                                                               92.7  0    100     92.7                                   3    "        232 2.3                                                                               65.5  0    70.6    92.7                                   Comp. A                                                                             W.sub.1.2 V.sub.3 Mo.sub.12 O.sub.x                                                     274 1.8                                                                               80.4  6.3  99.6    80.7                                   __________________________________________________________________________

In the same manner as shown by the examples above, other catalysts of the invention containing thorium instead of uranium or containing different amounts of uranium or thorium and different optional elements, such as Fe, Mn, Ni, Mg and the like, are used to produce acrylic acid. Moreover, promoted catalysts containing various amounts of tungsten, vanadium and molybdenum are used.

Also using the catalysts of the invention, maleic anhydride, methacrylic acid or acrylates are made by known oxidation reactions. 

We claim:
 1. A catalyst composition consisting essentially of oxides or oxide complexes having the empirical formula

    A.sub.a D.sub.b W.sub.c V.sub.d Mo.sub.e O.sub.x

wherein A is Co, Ni, Zn, Cu, Mg, Mn, Bi, Ti, Zr, Sn, P, Fe, an alkali metal an alkaline earth metal, an element of the lanthanoid series or mixture thereof; and D is thorium;and wherein a is 0 to about 5; b, c and d are about 0.1 to about 10; e is a number of about 6 to about 16; and x is the number of oxygens required to satisfy the valence requirements of the other elements present. 